1. Field of the Invention
This invention relates to systems for controlling vehicle traffic signals to allow safe passage of emergency vehicles and more particularly relates to a system for autonomously preempting traffic signals at an intersection that includes a transponder, a real-time intersection monitor, and an audio alarm or warning system.
2. Background Information
Present systems used to preempt traffic signals and clear intersections for emergency vehicles responding to a life-saving event rely on: sound activation, optical activation, direct microwave activation, and a combination of all the above. All of these systems have severe operational limitations affected by weather, line of sight, and critical range. These systems have further drawbacks requiring them to be activated by the emergency vehicle operator. None of these known systems provide real-time monitoring of intersection phases which has the added affect that an operator does not get the feedback desired and soon stops using the system.
Also emergency vehicles currently rely on vehicle horn, sirens, and flashing lights to prevent accidental collisions with pedestrians or other vehicles at intersections. An intersection-based system that would be activated remotely (and autonomously) by an approaching emergency vehicle is needed. Such a system overcomes some of these drawbacks of available systems by including an audible warning, most likely instructing nearby pedestrians to clear the intersection.
Visual displays at intersections may provide warnings to motorists and pedestrians yet they may fail to get the attention of pedestrian standing near an intersection. A visual sign may be barely visible at significant viewing angles and pedestrians will likely not be looking in the direction of any sign. For this reason, audible alerts in addition to visual may be the most effective (and rapid) warning system of the approach of emergency vehicles.
There is also the difficulty that pedestrians may often be in harms way if they fail to hear an approaching emergency vehicle. Although vehicle sirens are especially loud, many circumstances can lead to dangerous situations and potential injury. For instance, an especially long crosswalk may take up to 20 seconds to cross. In that time, an emergency vehicle may be heard, perhaps stranding the pedestrian in the middle of a crosswalk. Likewise, in extremely busy metropolitan intersections, ambient noise in the building occlusions may prevent warning of the emergency vehicle until just seconds before the vehicle arrived at an intersection. Previous experience with visual warning systems show that pedestrians are often unable to see the visual warning signs sufficiently during demonstrations.
It is one object of the present invention to provide an emergency vehicle traffic signal preemption system that is fully autonomous and not dependent on the intersection being in visual range.
Still another object of the present invention is to provide an emergency vehicle traffic signal preemption system that provides conflict detection and alerts other emergency vehicles in the area.
Still another object of the present invention is to provide an emergency vehicle traffic signal preemption system that includes a real-time monitor of intersection phase.
Yet another object of the present invention is to provide an emergency vehicle preemption system having an emergency vehicle transponder including an on-board diagnostic interface, a navigation interface, and a communications monitor and control interface.
Still another object of the present invention is to provide an improved emergency vehicle traffic signal preemption system including a real-time intersection status monitor.
Still another object of the present invention is to provide an emergency vehicle traffic signal preemption system that includes a pedestrian audio warning signal to supplement the visual display and the audio signals from emergency vehicles.